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The following abstract is that provided to first year undergraduate students as part of the recruitment effort for 1st Year Seminar Courses at the University of Guelph. When humankind begins the colonization of the moon or Mars, we will be bringing along more of Earth than one might think. A number of space and government agencies around the world, including researchers at the Controlled Environment Systems Research Facility, University of Guelph, are involved in the design and engineering of self-contained ecosystems based on Earthly biological processes. These processes can be harnessed, with complementary physical and chemical technologies to support human life (food production, air revitalization, psychology) in the hostile conditions of space.

This paper presents results generated from an EXCEL based static mass balance model for the incorporation of a higher plant chamber to the MELiSSA Pilot Plant. The model was parameterized using empirical data collected from beet and lettuce production trials and from trials conducted with Pilot Plant or bench scaled MELiSSA compartments. Of particular interest were the daily mass balances of CO2, O2 and nitrogen in the loop for a given set of input variables. The results allow the loop’s designers to foresee the range of conditions for which closure of the mass balances can be expected. This information will be used in the next phases of the MELISSA Pilot Plant integration project.

The MELISSA (Micro Ecological LIfe Support System Alternative) project of the European Space Agency (ESA) is a tool for the development of a simplified biological life support system. In order to achieve this purpose a loop of four interconnected bioreactors and a higher plant compartment has been designed. The target of the loop is to recycle the wastes, mainly CO2 and organic materials, generated in a closed environment such as in manned space missions, into oxygen, water and edible material. Light is the only energy source used to reach this goal. As a part of the development of the project, a Pilot Plant laboratory has been set up. The role of this pilot plant is to demonstrate the feasibility and robustness of the Melissa concept. In order to study the system two kinds of experiments are required. On one hand, each compartment has to be well characterized and, on the other hand, the performance of the connection between compartments has to be evaluated.

MELISSA (Micro Ecological Life Support System Alternative) is a research project for the development of advanced life support systems, conducted by the European Space Agency. Its basic design is based on a loop of bioreactors with the main objective of the regeneration of the wastes generated by a crew into an edible material, with concomitant regeneration of the atmosphere for human respiration. The MELISSA Pilot Plant is a European facility to study and validate advanced life support systems. It has as main objectives the ground demonstration and characterization of a closed loop concept. This includes the development of the associated technology for its successful continuous operation such as water treatment, pathogen detection, food preparation, and other related items. At present time, the main research project developed in the Pilot plant is the MELISSA project.

A biofiltration system was tested to remove low levels of acetone from an indoor space. The biofilters were subjected to a range of air fluxes and concentrations of acetone between 100 and 500 ppbv. Passing low levels of acetone through a canopy of green plants did not improve the quality of the air. However, acetone removal by the biofilters with living moss as a principle substrate, reached a maximum of between 1 and 1.6 μmol s-1 m-2 with a loading rate of approximately 2 μmol s-1 m-2. Generally the removal efficiency decreased with increased loading rates over a range of air fluxes (0.05 to 0.2 m s-1) but appear to increase with loading within the slower fluxes. Neither ZERO nor FIRST order kinetics could adequately describe removal. Instead an empirical model that described the natural logarithm of the unloading rate as a function of the natural logarithm of the loading rate and the natural logarithm of the inverse of the air flux fit the data well.

A deterministic model of canopy CO, exchange for a soybean crop has been developed to describe vegetative and reproductive phases of growth. Using this profile as an example, a conceptual model for the design and management of integrated production systems is developed with the objective of dampening both the long term and photo-oscillatory gas exchange dynamics of plant canopies in sealed environments. The resulting conceptual model includes photoperiod offset coupled with staggered planting and attenuated lighting as operational means of achieving stable atmospheric CO, concentrations. The issue of cultural compatibility of crops for integrated production is discussed and an operational scenario is proposed for two production chambers having different crop compositions and photoperiod requirements. The resulting operational scenarios have application to large scale, planetary based bioregenerative life support systems.

A biofiltration system is currently being tested as an alternative to maintain indoor air quality within an office building setting. The system is based on a complex plant community with both terrestrial and aquatic components. CO2 dynamics within the space offer a means of evaluating its potential efficacy. A model is presented based upon both exponential and linear processes, which accurately describes diurnal changes in CO2 levels and the removal of introduced CO2. The exponential dynamics indicate increasing rates of sequestering with increasing exposure levels. The CO2 is eventually fixed through the process of photosynthesis, but is most likely initially sequestered in the aquatic component of the system. The removal of the contaminant from the atmosphere and into the aquatic phase where it is subsequently metabolized by the biomass suggest the system may be an effective filter for removing contaminants from indoor settings.

Successful implementation of the MELISSA loop requires the optimum performance of each of its compartments. Preliminary studies on the behaviour of the photoheterotrophic compartment have been performed. The previously suggested strains have been tested for growth on the carbon and nitrogen sources expected to be components of the influent. The results indicate that of the organisms tested Rs.rubrum should become the organism of choice for the photoheterotrophic compartment while R.capsulatus is more appropriate for the photoautotrophic anaerobic compartment. Biomass analyses, determination of yields and growth rates have also been performed in the preliminary batch and continuous cultures.